class DataLogger:
"""Logs data from the magenetomer for implementing the calibration levels"""
def __init__(self, magnetometer=None):
if magnetometer == None:
self.magnetometer = Magnetometer()
else:
self.magnetometer = magnetometer
self.x = []
self.y = []
self.z = []
def measure(self, num_readings, time_ms_per_reading=0):
"""time per reading must be more than 7 ms"""
if (time_ms_per_reading > 7):
time_sleep = time_ms_per_reading - 7
for i in range(num_readings + 2):
self.magnetometer.take_measurement()
if i > 1:
self.x.append(self.magnetometer.x)
self.y.append(self.magnetometer.y)
self.z.append(self.magnetometer.z)
sleep_ms(time_sleep)
else:
for i in range(num_readings):
self.magnetometer.take_measurement()
if i > 1:
self.x.append(self.magnetometer.x)
self.y.append(self.magnetometer.y)
self.z.append(self.magnetometer.z)
def get_json(self):
data["x"] = self.x
data["y"] = self.y
data["z"] = self.z
return ujson.dumps(data)
def std_dev(self):
mean = sum(self.z) / len(self.z)
z = math.sqrt(
sum(map(lambda x: (x - mean) * (x - mean), self.z)) / len(self.z))
mean = sum(self.y) / len(self.y)
y = math.sqrt(
sum(map(lambda x: (x - mean) * (x - mean), self.y)) / len(self.y))
mean = sum(self.x) / len(self.x)
x = math.sqrt(
sum(map(lambda x: (x - mean) * (x - mean), self.x)) / len(self.x))
return (x, y, z)
class DataLogger:
"""
Logs data from the magenetometer
"""
def __init__(self, magnetometer=None):
"""
Creates a DataLogger instance, optionally uses a Magnetometer instance if given, otherwises creates a new
instance
:param magnetometer: the optional magnetometer instance it will use to record data
"""
if magnetometer == None:
self.magnetometer = Magnetometer()
else:
self.magnetometer = magnetometer
self.data = []
def measure(self, num_readings, time_ms_per_reading=0):
"""
Takes reading from the magnetometer and scales to the correct units
:param num_readings: number of readings to take
:param time_ms_per_reading: time to spend taking each reading
:return: no return value
"""
self.data = []
"""time per reading must be more than 7 ms"""
if (time_ms_per_reading > 7):
time_sleep = time_ms_per_reading - 7
for i in range(num_readings + 2):
self.magnetometer.take_measurement()
if i > 1:
vector = Vector3D()
vector.x = self.magnetometer.x
vector.y = self.magnetometer.y
vector.z = self.magnetometer.z
self.data.append(vector)
sleep_ms(time_sleep)
else:
for i in range(num_readings):
self.magnetometer.take_measurement()
if i > 1:
vector = Vector3D()
vector.x = self.magnetometer.x
vector.y = self.magnetometer.y
vector.z = self.magnetometer.z
self.data.append(vector)
if num_readings >= 10:
self.data = self.data[5:]
def get_json(self):
"""
Converts recorded magnetometer data to JSON
:return: JSON object containing magnetometer readings
"""
return ujson.dumps(self.data)
def mean(self):
"""
Calculates the mean of the recorded data
:return: Vector3D instance of the mean value recorded in each axis
"""
if self.data == []:
print("Take measurement first using measure()")
return 0
self.data_mean = Vector3D()
for i in self.data:
self.data_mean = self.data_mean + i
self.data_mean = self.data_mean.mul(1 / len(self.data))
return self.data_mean
def std_dev(self):
"""
Calculate the standard deviation of the recorded data
:return: Vector3D instance of the std deviation value recorded in each axis
"""
self.mean()
res = Vector3D()
for i in range(len(self.data)):
res = res + (self.data[i] - self.data_mean) * (self.data[i] -
self.data_mean)
res = res.mul(1 / len(self.data))
res = res.sqrt()
self.data_std_dev = res
return res